Dextromethorphan (DXM or DM) is an antitussive drug. It is one of the active ingredients used to prevent coughs in many over-the-counter cold and cough medicines. Dextromethorphan has also found other uses in medicine, ranging from pain relief to psychological applications. It is sold in syrup, tablet, spray, and lozenge forms manufactured under several different brand names and generic labels. In its pure form, dextromethorphan occurs as a white powder.When exceeding label-specified maximum dosages, dextromethorphan acts as a dissociative psychedelic drug. Its mechanism of action is as an NMDA receptor antagonist, producing effects similar to those of the controlled substances ketamine and phencyclidine (PCP).